1. Technical Field
The present invention relates to the field of electronic signal analyzers, and more particularly to non-contact signal analyzers for detecting the presence and transmission protocol of network signals.
2. Background Art
It is known to transmit electronic voice, video, and data signals through communications networks, such as the public switched telephone network (PSTN), the internet, and private local area and wide area networks (LANs and WANs). The network communications medium may be wireline, such as coaxial cable, twisted pair, or fiber optic cable, or wireless, such as cellular or radio frequency (RF) transmission. The majority of installed networks are wireline, and the most common type wireline is unshielded, twisted pair copper wire.
In operation, the networks provide simultaneous shared access by different users, and the signals appear in both digital and analog format; often together, such as in the PSTN where they are transmitted simultaneously in different segments of the network""s frequency bandwidth. Also, the different network digital devices, such as computers, telephones, and video displays, have different signal bandwidth (bit per second) requirements. They may even have different transmission and reception signal bandwidths, as in the case of internet communications or data retrieval operations, where the download data volume far exceeds the upload commands. This is accommodated by using different digital transmission protocols, such as asymmetrical digital subscriber line (ADSL) and integrated-services digital network (ISDN), which PSTN service providers use for internet communications. In summary, a single conductor pair may simultaneously carry several full duplex signal exchanges, each at different frequency bandwidth segments, with different digital signal bandwidths, and possibly combined analog and digital format.
Networks, other than LANs, are interconnected to provide out of network communications. The interconnections are provided through the use of bridges and/or routers for the internet protocol (IP) networks, and by local and central office telephone switches for the PSTN. All of the interconnected network signal traffic flows through these switch points. Since it is necessary to monitor network signal traffic to determine performance trends or to isolate and repair failures, it is necessary for both IP network and telephone technicians to sample the network signal traffic at different locations to determine traffic patterns, but also to analyze the waveform characteristics of the transmitted signals for purposes of quality control. This quality monitoring includes the auditing of the transmission fidelity of particular digital signal protocols.
The prior art discloses various types of signal analyzers which determine the presence and transmission protocol of network signals. The manner in which these analyzers access the network signals varies. Some are invasive in that the sensor makes physical electrical contact with the conductor pairs by piercing the wire insulation with pointed probes. One such type used by telephone network technicians is referred to as a xe2x80x9cbed of nailsxe2x80x9d in that it includes a number of fixture mounted probes which engage and make physical contact with the conductor wires. This physical contact creates signal noise which may manifest itself to the network user as audible sounds in the case of audio signal transmission or which may result in noise interference sufficient to interrupt and terminate a digital signal transmission. While audible interference may be annoying, the termination of a digital transmission and resulting loss of data may have much greater consequences.
There are also prior art non-contact sensors which inductively couple the transmission signal from the conductor pair, avoiding the problems resulting from physical connection. The inductively coupled sensors, however, also have disadvantages. One disadvantage is its limited signal sensitivity. These are current sensitive devices which are appropriate for use in detecting high current signals, but have limited use in low power signal detection such as is the case with network and telephone signals. A second disadvantage is the back electromagnetic force (emf) generated by the pick-up inductor (or coil) into the signal stream. This appears as noise on the line, which has the possibility of disrupting the signal or distorting its waveshape.
There is, therefore, a need for a signal sensor capable of acquiring for a signal analyzer, high fidelity samples of the transmitted signal waveforms on twisted pair conductors.
One object of the present invention is to provide an analyzer sensor capable of providing a signal analyzer with high fidelity waveform samples of twisted pair network signals. Another object of the present invention is to provide such a high fidelity analyzer sensor with the further characteristic of its ease of use in connecting to a twisted pair of conductors. Still another object of the present invention is to provide such an analyzer sensor with the capability of achieving a high integrity connection to a twisted pair of conductors. Still another object of the present invention is to provide such an analyzer sensor which is capable of portable use.
According to one aspect of the present invention, an analyzer sensor detects signal waveforms on a pair of conductors and provides amplification of the difference of the first and second signal waveforms. In further accord with the invention, the invention includes a first and second capacitive coupler, each connected to an associated termination impedance and each adapted for placement adjacent to a related one of the two conductors to capacitively couple first and second sample signals, respectively, of the signal waveforms from the related conductor to the associated termination impedance. In still further accord with the invention, the invention includes a first and second buffer amplifier responsive, respectively, to the first and second sample signals at the termination impedances of the first and second capacitive couplers, for providing at a first and second output thereof, respectively, an amplified difference of the first and second sample signals. Additionally, in further accord with the invention, the invention includes a utility module which includes a battery source connected to the buffer amplifiers by a line for providing power to the buffer amplifiers at a location distant from the buffer amplifiers.
According to a second aspect of the present invention, the analyzer sensor includes first and second capacitive coupler, each connected to a termination impedance and adapted for placement adjacent to a related one of the two conductors to capacitively couple first and second sample signals, respectively, of the signal waveforms from the related conductor to the associated termination impedance. In further accord with the invention, the invention includes a first and second buffer amplifier responsive, respectively, to the first and second sample signals at the termination impedances of the first and second capacitive couplers, for providing first and second conditioned signals at a first and second output thereof. In still further accord with the invention, the invention includes a third and fourth buffer amplifier including first and second inputs responsive to the first and second conditioned signals, respectively, for providing, at a third and fourth output thereof, respectively, an amplified difference of the first and second conditioned signals.
According to a third aspect of the invention, the analyzer sensor includes a housing for enclosing the capacitive couplers and buffer amplifiers. The capacitive couplers being adapted to be placed by an operator in proximity to one or more conductors. In further accord with the invention, the housing has recesses on its surface where capacitive couplers are each in registration. In still further accord with the invention, the housing includes clamp assemblies for holding each conductor in registration with the associated coupler.
According to a fourth aspect of the present invention, the battery source of the analyzer sensor includes a voltage source for supplying power to the buffer amplifiers. In further accord with the invention, the battery source includes a regulator connected to the voltage source and adapted to measure and respond to low voltage at the voltage source. In still further accord with the invention, the battery source further includes indicators connected to the regulator indicating the presence of low voltage at the voltage source.